Tutorial - First Steps¶

Phase 1: Testing¶

To test the DC Brick you need to have the Brick Daemon and the Brick Viewer installed (for installation guides click here and here). The Brick Viewer has to be connected to the Brick Daemon, click the "Connect" button in Brick Viewer to ensure this.

The Brick Daemon is a bridge between the Bricks/Bricklets and the programming language specific API bindings. It provides a graphical interface for testing purposes.

After the installation you are ready to tinker! Take the DC Brick and connect a motor and a battery, as shown the picture below. Of course you can also use a power supply instead of the battery or e.g. a Servo Brick and a servo instead of the DC Brick and a motor:

Now connect the Brick to the PC over USB, you should see a new tab named "DC Brick" in the Brick Viewer after a moment. Select this tab. Your Brick Viewer should now show the interface depicted below:

You can see the voltage of the connected battery as "External Voltage" and the current used by the motor as "Current Consumption" as well as a representation of the current velocity on the right side. Different sliders allow you to modify velocity and acceleration of the motor as well as the PWM frequency of the driver. After clicking "Enable DC Motor" you are in control of the motor.

Phase 2: Write your own Program¶

The DC Brick and motor are verified to work properly, there is now nothing in the way to write a first program that controls the DC Brick.

You can choose one of the available programming languages, in this tutorial we use Python.

The necessary steps to get everything working are essentially the same in all programming language. This tutorial together with the examples in the API documentation of every product should allow you to get any Brick working with any programming language.

In the following we assume that you now the basics of the programming language you picked and that the necessary compilers/interpreters are already installed.

First, install the API bindings for your programming languages. Installation instructions for all API bindings can be found here.

Now create a folder for your DC Brick test project. Download one of the examples for the DC Brick from here as a starting point and place it in the folder.

In this tutorial we take a look at example_configuration.py:

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID = "XXYYZZ" # Change XXYYZZ to the UID of your DC Brick

import time

from tinkerforge.ip_connection import IPConnection
from tinkerforge.brick_dc import BrickDC

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    dc = BrickDC(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    dc.set_drive_mode(dc.DRIVE_MODE_DRIVE_COAST)
    dc.set_pwm_frequency(10000) # Use PWM frequency of 10 kHz
    dc.set_acceleration(4096) # Slow acceleration (12.5 %/s)
    dc.set_velocity(32767) # Full speed forward (100 %)
    dc.enable() # Enable motor power

    input("Press key to exit\n") # Use raw_input() in Python 2

    # Stop motor before disabling motor power
    dc.set_acceleration(16384) # Fast decceleration (50 %/s) for stopping
    dc.set_velocity(0) # Request motor stop
    time.sleep(2) # Wait for motor to actually stop: velocity (100 %) / decceleration (50 %/s) = 2 s
    dc.disable() # Disable motor power

    ipcon.disconnect()

Line 14 creates an IP Connection object.

Line 15 creates an object that allows us to control the DC Brick. It is necessary to pass the Unique Identifier (UID) of the Brick (in this example defined in Line 6) and the ipcon object. Change the UID corresponding to your device!

In Line 17 the IP Connection is connected. It is possible to run your program on another PC than the one which has the Brick Daemon running (e.g. you can write a program for your smart phone that controls a Brick connected to your PC).

The Lines 20-24 configure the DC Brick and let the motor run forwards at full speed.

Line 26 is used to prevent program termination until you press enter.

Line 29-32 stops the motor before the program ends.

Run this Python script and use it or other examples as a starting point for your own project.

Phase 1: Testing¶

Connect the Rotary Poti Bricklet to your DC Brick as depicted in the image below.

If you now connect the DC Brick to the PC, not only a "DC Brick" tab but also a "Rotary Poti Bricklet" tab will be shown in the Brick Viewer. Select the "Rotary Poti Bricklet" tab and rotate the potentiometer. You should see a corresponding movement in the viewer.

Phase 2: Write your own Program¶

To incorporate the Rotary Poti Bricklet in our small project we change the program to allow controlling the motor velocity with the rotary poti: (Download):

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID_DC = "XXYYZZ" # Change to the UID of your DC Brick
UID_POTI = "XYZ" # Change to the UID of your Rotary Poti Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.brick_dc import BrickDC
from tinkerforge.bricklet_rotary_poti import BrickletRotaryPoti

dc = None

# Callback function for position callback (parameter has range -150 to 150)
def cb_position(position):
    velocity = 32767 // 2 * position // 150 # Velocity: -32767/32767

    print('Set Position/Velocity: ' + str(position) + '/' + str(velocity))

    dc.set_velocity(velocity)

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection

    dc = BrickDC(UID_DC, ipcon) # Create DC brick device object
    poti = BrickletRotaryPoti(UID_POTI, ipcon) # Create rotary poti device object

    ipcon.connect(HOST, PORT) # Connect to brickd

    poti.set_position_callback_period(50) # set callback period to 50ms
    poti.register_callback(poti.CALLBACK_POSITION, cb_position)

    dc.enable() # Enable motor power
    dc.set_acceleration(0xFFFF) # Full acceleration

    input('Press Enter to exit\n') # Use raw_input() in Python 2

    # Stop motor before disabling motor power
    dc.set_acceleration(16384) # Fast decceleration (50 %/s) for stopping
    dc.set_velocity(0) # Request motor stop
    time.sleep(2) # Wait for motor to actually stop: velocity (100 %) / decceleration (50 %/s) = 2 s
    dc.disable() # Disable motor power

    ipcon.disconnect()

Lines 4-7 are the typical configurations, the UID has to be changed according to the Bricks and Bricklets you use.

In Lines 24-29 an IP Connection to the Brick Daemon is established and the Brick and Bricklet device objects are created.

We configure the Rotary Poti Bricklet, to call the function cb_position every time the position of the potentiometer changes. Line 31 configures this callback to be triggered with a period of 50ms if the position changes. If the position is unchanged there won't be any callbacks. This is an efficient implementation, only the bare minimum of USB bandwidth is used. The callback function is registered in Line 32. cb_position is defined in Lines 16-21, it sets a new velocity based on the current position of the potentiometer.

In Lines 34-35 we enable the motor and set a maximum acceleration. This allows the motor to follow the potentiometer movements immediately.

In Lines 37 we wait for user input to prevent program termination.

Line 40-43 stops the motor before the program ends.

Phase 1: Testing¶

Build a stack consisting of a Step-Down Power Supply with connected battery, a Master Brick with connected Rotary Poti Bricklet and a DC Brick with connected motor (from bottom to top).

This setup is depicted in the image below.

If you connect the Master Brick to the PC over USB, the Brick Viewer should show the Master Brick (measuring current and voltage flowing through the stack), the DC Brick and the Rotary Poti Bricklet.

Phase 2: Write your own Program¶

Since the stacking is transparent you are able to run the program of the previous part without any changes!